U.S. patent application number 12/256367 was filed with the patent office on 2009-04-23 for liquid jetting apparatus.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Yuichi Nishihara.
Application Number | 20090102903 12/256367 |
Document ID | / |
Family ID | 40563085 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090102903 |
Kind Code |
A1 |
Nishihara; Yuichi |
April 23, 2009 |
Liquid Jetting Apparatus
Abstract
A liquid jetting apparatus for jetting electrically conductive
liquid onto a medium includes a liquid reservoir section, a sensor
and a conductive member. The liquid reservoir section stores the
liquid. The sensor is disposed at a location in the liquid
reservoir section, for electrically detecting the condition of the
liquid at the location. The conductive member contacts the
conductive liquid and that is electrically connected to a stable
potential.
Inventors: |
Nishihara; Yuichi;
(Matsumoto-shi, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
1999 AVENUE OF THE STARS, SUITE 1400
LOS ANGELES
CA
90067
US
|
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
40563085 |
Appl. No.: |
12/256367 |
Filed: |
October 22, 2008 |
Current U.S.
Class: |
347/86 |
Current CPC
Class: |
B41J 2/17566 20130101;
B41J 2002/17579 20130101; H05K 3/1241 20130101 |
Class at
Publication: |
347/86 |
International
Class: |
B41J 2/175 20060101
B41J002/175 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2007 |
JP |
2007-275463 |
Sep 25, 2008 |
JP |
2008-245935 |
Claims
1. A liquid jetting apparatus for jetting electrically conductive
liquid onto a medium, the liquid jetting apparatus comprising: a
liquid reservoir section that stores the conductive liquid; a
sensor disposed at a location in the liquid reservoir section, for
electrically detecting a condition of the conductive liquid at the
location; and a conductive member that contacts the conductive
liquid and that is electrically connected to a stable
potential.
2. A liquid jetting apparatus in accordance with claim 1, wherein
the conductive member is present in proximity to the sensor.
3. A liquid jetting apparatus in accordance with claim 1,
comprising: a liquid jetting section; and a liquid container that
includes the liquid reservoir section and the sensor, the liquid
container being detachably installed in the liquid jetting
section.
4. A liquid jetting apparatus in accordance with claim 1
comprising: a liquid jetting section that includes the sensor and
part of the liquid reservoir section; and a liquid container that
includes another part of the liquid reservoir section, the liquid
container being detachably installed in the liquid jetting
section.
5. A liquid jetting apparatus for jetting electrically conductive
liquid onto a medium, the liquid jetting apparatus comprising: a
liquid reservoir section that stores the conductive liquid; a
sensor disposed at a location in the liquid reservoir section, for
electrically detecting a condition of the conductive liquid at the
location; and an electrostatic capacitance provided between a
stable potential and the liquid, the electrostatic capacitance
reducing extrinsic noise.
6. A liquid jetting apparatus in accordance with claim 5, wherein
the electrostatic capacitance is present between the stable
potential and the liquid in proximity to the sensor.
7. A liquid jetting apparatus in accordance with claim 5,
comprising: a liquid jetting section; and a liquid container that
includes the liquid reservoir section and the sensor, the liquid
container being detachably installed in the liquid jetting
section.
8. A liquid jetting apparatus in accordance with claim 5
comprising: a liquid jetting section that includes the sensor and
part of the liquid reservoir section; and a liquid container that
includes another part of the liquid reservoir section, the liquid
container being detachably installed in the liquid jetting
section.
9. A liquid jetting apparatus in accordance with claim 1, wherein
the stable potential is a frame ground of the liquid jetting
apparatus.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application relates to and claims priority from
Japanese Patent Application No. 2007-275463, filed on Oct. 23,
2007, and No. 2008-245935, filed on Sep. 25, 2008 the entire
disclosure of which is incorporated by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a liquid jetting apparatus,
in particular to a liquid jetting apparatus adapted to jet
electrically conductive liquid onto a medium.
[0004] 2. Description of the Related Art
[0005] Ink-jet printers adapted for installation of one or more ink
cartridges containing ink and to carry out printing onto a printing
medium by consuming the ink supplied from the ink cartridges are
known in the art. Ink cartridges of this kind equipped with a
sensor for electrically sensing the condition of consumption of ink
contained therein are also known in the art.
[0006] However, if an ink has electrical conductivity, extraneous
noise may interfere through the medium of the ink, posing the risk
of diminished sensing accuracy of the sensor. This issue is not
limited to ink-jet printers, but is a problem common to liquid
jetting apparatus, for example, apparatus for jetting a liquid
material containing a metal component onto a semiconductor in order
to form the electrode layer.
SUMMARY
[0007] It is accordingly one object of the present invention to
limit interference, through the medium of the ink, with a sensor
that electrically detects the condition of a conductive liquid such
as ink.
[0008] A first aspect of the invention provides a liquid jetting
apparatus for jetting electrically conductive liquid onto a medium.
The liquid jetting apparatus of the first aspect comprises a liquid
reservoir section, a sensor and a conductive member. The liquid
reservoir section stores a conductive liquid. The sensor is
disposed at a location in the liquid reservoir section, for
electrically detecting a condition of the conductive liquid at the
location. The conductive member contacts the conductive liquid and
is electrically connected to a stable potential.
[0009] According to the liquid jetting apparatus of the first
aspect, the conductive liquid is connected to a stable potential,
thereby reducing interference of extraneous noise with the sensor
through the medium of the conductive liquid. The sensing accuracy
of the sensor may be improved as a result, for example.
[0010] In the liquid jetting apparatus pertaining to the first
aspect, the conductive member may be present proximity to the
sensor. In this case, interference by extraneous noise may be
reduced more effectively.
[0011] The liquid jetting apparatus pertaining to the first aspect
may comprise a liquid jetting section and a liquid container that
includes the liquid reservoir section and the sensor, the liquid
container being detachably installed in the liquid jetting section.
The liquid jetting apparatus pertaining to the first aspect may
comprise a liquid jetting section that includes the sensor and part
of the liquid reservoir section and a liquid container that
includes another part of the liquid reservoir section, the liquid
container being detachably installed in the liquid jetting
section.
[0012] A second aspect of the invention provides a liquid jetting
apparatus for jetting electrically conductive liquid onto a medium.
The liquid jetting apparatus of the first aspect comprises a liquid
reservoir section, a sensor and an electrostatic capacitance. The
liquid reservoir section stores the conductive liquid. The sensor
is disposed at a location in the liquid reservoir section, for
electrically detecting a condition of the conductive liquid at the
location. The electrostatic capacitance is provided between a
stable potential and the liquid, the electrostatic capacitance
reducing extrinsic noise.
[0013] According to the liquid jetting apparatus of the second
aspect, the conductive liquid is AC connected to a stable potential
through electrostatic capacitance, thereby reducing interference of
the AC component of extraneous noise with the sensor through the
medium of the conductive liquid. The sensing accuracy of the sensor
may be improved as a result, for example.
[0014] In the liquid jetting apparatus pertaining to the second
aspect, the electrostatic capacitance may be present between the
stable potential and the liquid in proximity to the sensor. In this
case, interference by extraneous noise may be reduced more
effectively.
[0015] The liquid jetting apparatus pertaining to the second aspect
may comprise a liquid jetting section and a liquid container that
includes the liquid reservoir section and the sensor, the liquid
container being detachably installed in the liquid jetting section.
The liquid jetting apparatus pertaining to the second aspect may
comprise a liquid jetting section that includes the sensor and part
of the liquid reservoir section and a liquid container that
includes another part of the liquid reservoir section, the liquid
container being detachably installed in the liquid jetting
section.
[0016] In the liquid jetting apparatus pertaining to the second
aspect, the stable potential may be the frame ground of the liquid
jetting apparatus.
[0017] The above and other objects, characterizing features,
aspects and advantages of the invention will be clear from the
description of preferred embodiments presented below along with the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an illustration depicting a simplified
configuration of a printing system in first embodiment;
[0019] FIG. 2 is a diagram depicting an ink cartridge attached to a
print head unit;
[0020] FIG. 3 is a first exterior perspective view of an ink
cartridge in first embodiment;
[0021] FIG. 4 is a second exterior perspective view of an ink
cartridge in the first embodiment;
[0022] FIG. 5 is a first exploded perspective view of an ink
cartridge in the first embodiment;
[0023] FIG. 6 is a second exploded perspective view of an ink
cartridge in the first embodiment;
[0024] FIG. 7 is a conceptual depiction of the pathway leading from
the open air hole to the liquid supply portion;
[0025] FIG. 8 is a diagram of the cartridge body viewed from the
front;
[0026] FIG. 9 is a diagram of the cartridge body viewed from the
back;
[0027] FIG. 10A is simplified schematic of FIG. 8;
[0028] FIG. 10B is simplified schematic of FIG. 9;
[0029] FIG. 11 is a diagram illustrating the configuration of the
sensor portion in the first embodiment;
[0030] FIG. 12 is a diagram of the electrical configuration
centered on a piezoelectric device that included in the sensor in
the first embodiment;
[0031] FIG. 13 is a diagram of an electrical configuration centered
on a piezoelectric device that constitutes the sensor in the
comparative example;
[0032] FIG. 14 is a diagram depicting a simplified cross section of
construction in an area from the vicinity of the differential
pressure regulating valve to the liquid supply portion 50, shown
together with a simplified cross section of the print head;
[0033] FIG. 15 is a diagram illustrating the configuration of the
sensor portion in second embodiment;
[0034] FIG. 16 is a diagram of the electrical configuration
centered on a piezoelectric device that constitutes the sensor in
the second embodiment;
[0035] FIG. 17 is an exploded perspective view of an ink cartridge
in a variation of the second embodiment;
[0036] FIG. 18 is a diagram of the electrical configuration
centered on a piezoelectric device that constitutes the sensor in
the variation of the second embodiment;
[0037] FIG. 19 depicts a hermetic type ink cartridge in front view
and in side view;
[0038] FIG. 20 is a first diagram depicting the B-B cross section
in FIG. 19; and
[0039] FIG. 21 is a second diagram depicting the B-B cross section
in FIG. 19.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] Next, the preferred embodiments for carrying out the
invention will be described based on the accompanying drawings.
A. First Embodiment
[0041] Printer and Ink Cartridge Configuration:
[0042] The configuration of a printer according to a first
embodiment will be described with reference to FIGS. 1 and 2. FIG.
1 is an illustration depicting a simplified configuration of a
printing system in first embodiment. FIG. 2 is a diagram depicting
an ink cartridge attached to a print head unit.
[0043] The printing system includes a printer 1000 and a computer
2000. The printer 1000 is connected to the computer 2000 through a
connector CN.
[0044] The printer 1000 is equipped with a sub-scan feed mechanism,
a main scan feed mechanism, a head driving mechanism, and a main
controller 2 for controlling these mechanisms. The sub-scan feed
mechanism includes a paper feed motor 3 and a platen 4, and
functions to transport paper P in the sub-scanning direction
through transmission of the rotation of the paper feed motor to the
platen. The main scan feed mechanism includes a carriage motor 5, a
pulley 7, a drive belt 8 stretched between the carriage motor 5 and
the pulley 7, and a slide rail 9 disposed parallel to the axis of
the platen. The slide rail 9 slidably retains a carriage 6 that is
affixed to the drive belt 8. Rotation of the carriage motor 5 is
transmitted to the carriage 6 via the drive belt 8, whereby the
carriage 6 reciprocates in the axial direction of the platen 4 (the
main scanning direction)along the slide rail 9. The head driving
mechanism includes a print head unit 60 that rests on the carriage
6; the print head is driven in order to eject ink onto the paper P.
Above the print head unit 60 is disposed a holder (not shown in
FIG. 1), discussed later, adapted for detachable installation of
plurality of ink cartridges. The printer 1000 is additionally
includes an operation section enabling the user to make various
settings or check the printer status; however, these need not be
discussed in detail.
[0045] As depicted in FIG. 2, the print head unit 60 includes a
print head 61, and a holder 62 situated on the upper face of the
print head 61. The holder 62 is designed to accommodate
installation of several ink cartridges 1. Projections 63 and
recessed portions 64 are formed in the holder 62 for the purpose of
positioning and fastening the ink cartridges 1. A carriage circuit
and a connection mechanism having connecting pins (terminals) (not
shown) are disposed at the aperture 65 of the holder 62 towards the
negative direction along the X axis. Ink supply needles, discussed
later, are disposed on the upper face to the print head 61.
[0046] Referring now to FIGS. 3 to 6 in addition to FIG. 2, the ink
cartridges 1 will be discussed further. FIG. 3 is a first exterior
perspective view of an ink cartridge in first embodiment. FIG. 4 is
a second exterior perspective view of an ink cartridge in first
embodiment. The drawing in FIG. 4 is viewed from the opposite
direction from than in FIG. 3. FIG. 5 is a first exploded
perspective view of an ink cartridge in first embodiment. FIG. 6 is
a second exploded perspective view of an ink cartridge in first
embodiment. The drawing in FIG. 6 is viewed from the opposite
direction from than in FIG. 5.
[0047] The ink cartridge 1 contains a conductive liquid ink inside.
With the ink cartridge 1 installed in the holder 2 as depicted in
FIG. 2, the ink will be supplied to the print head 61 through the
ink supply needle.
[0048] As depicted in FIGS. 3 and 4, the ink cartridge 1 has a
generally rectangular parallelepiped shape having a face 1e on the
Z axis positive direction side, a face 1f on the Z axis negative
direction side, a face 1g on the X axis positive direction side, a
face 1h on the X axis negative direction side, a face 1i on the Y
axis positive direction side, and a face 1j on the Y axis negative
direction side. Hereinbelow, for convenience in discussion, face 1e
shall be termed the upper face; face 1f the lower face; face 1g the
right face; face 1h the left face; face 1i the front face; and face
1j the back face. The sides at which these faces 1e to 1j are
located shall be termed the upper face side, the lower face side,
the right face side, the left face side, the front face side, and
the back face side, respectively.
[0049] On the lower face 1f is provided a liquid supply portion 50
having a supply hole for supplying ink to the ink-jet printer.
Additionally, an open air hole 100 allowing air to be introduced
into the ink cartridge 1 opens onto the bottom face 1f (FIG.
6).
[0050] The open air hole 100 is formed with a depth and diameter
such that it will mate, with enough leeway to form a prescribed
gap, with one of the projections 63 (FIG. 2) that have been formed
on the print head unit 60 of the ink-jet printer. The user will
remove a sealing film 90 that air-tightly seals the open air hole
100, then install the ink cartridge 1 in the holder 62. The
projection 63 has the function of preventing the user from
forgetting to remove the sealing film 90.
[0051] A locking lever 11 is provided on the left side face 1h. A
projection 11a is formed on the locking lever 11. With the ink
cartridge 1 installed in the holder 62, the projection 11a will
mate with one of the recessed portions 64 of the holder 62 thereby
fastening the ink cartridge 1 to the holder 62 (FIG. 2).
[0052] A circuit board 34 is disposed below the locking lever 11 of
the left side face 1h (FIG. 4). A number of electrode terminals 34a
are formed on the circuit board 34; these electrode terminals 34a
provide electrical connection to the carriage circuit via a
connecting mechanism (not shown) that has been provided to the
carriage 6.
[0053] An outside surface film 55 is adhered to the upper face 1e
and the back face 1j of the ink cartridge 1.
[0054] The internal construction and parts configuration of the ink
cartridge 1 will now be described with reference to FIGS. 5 and 6.
The ink cartridge 1 has a cartridge body 10 and cover member 20
that covers the front face side of the cartridge body 10.
[0055] Ribs 10a of various shapes are formed on the front face side
of the cartridge body 10 (FIG. 5). Between the cartridge body 10
and the cover member 20 is disposed a film 80 covering the front
face side. The film 80 adheres intimately so as to prevent gaps
from forming at the front face-side edges of the ribs 10a of the
cartridge body 10. These ribs 10a and the film 80 define within the
interior of the ink cartridge 1 a number of small chambers, for
example, an ink reservoir chamber and a buffer chamber, to be
discussed later.
[0056] A differential pressure regulating valve housing chamber 40a
and a gas-liquid separation chamber 70a are formed at the back face
side of the cartridge body 10 (FIG. 6). The differential pressure
regulating valve housing chamber 40a houses a differential pressure
regulating valve 40 that is composed of a valve member 41, a spring
42, and a spring seat 43. A dike 70b is formed on the inside wall
that encloses the gas-liquid separation chamber 70a; and a
gas-liquid separation membrane 71 is adhered to the dike 70b, with
the structure as a whole constituting a gas-liquid separation
filter 70.
[0057] Additionally, a number of grooves 10b are formed on the back
end side of the cartridge body 10 (FIG. 6). When the outside
surface film 55 is adhered to the cartridge body 10 so as to cover
substantially the entire back face side thereof, these grooves 10b
will define various passages, discussed later, between the
cartridge body 10 and the outside surface film 55. The passages are
for ink and air to flow through.
[0058] Next, the construction of the circuit board 34 mentioned
above and surrounding area will be described. A sensor housing
chamber 30a is formed at the lower face side of the left side face
of the cartridge body 10 (FIG. 6). A remaining liquid level sensor
module 31 and a fastening spring 32 are housed within the sensor
housing chamber 30a. The fastening spring 32 presses the remaining
liquid level sensor module 31 against the inside wall at the lower
face side of the sensor housing chamber 30a, securing it in place.
An opening on the right face side of the sensor housing chamber 30a
is covered by a cover member 33, and the circuit board 34 mentioned
above is fastened to the outside surface 33a of the cover member
33. The sensor housing chamber 30a, the remaining liquid level
sensor module 31, the fastening spring 32, the cover member 33, the
circuit board 34, and a sensor channel defining chamber 30b to be
discussed later shall be referred to into to as a sensor portion
30.
[0059] The circuit board 34 will be provided with a rewriteable
nonvolatile memory such as EEPROM (Electronically Erasable and
Programmable Read Only Memory), which records information such as
the amount of ink consumption by the ink-jet printer.
[0060] On the lower face side of the cartridge body 10 there are
provided, in addition to the liquid supply portion 50 and the open
air hole 100 mentioned previously, a pressure release hole 110, the
sensor channel defining chamber 30b, and a labyrinth channel
defining chamber 95a (FIG. 6). The pressure release hole 110 is
used to suck out air in order release pressure inside the ink
cartridge 1 during injection of ink into the ink cartridge 1 in the
manufacturing process. The sensor channel defining chamber 30b and
the labyrinth channel defining chamber 95a define part of an ink
reservoir portion, discussed later.
[0061] Immediately after manufacture of the ink cartridge 1, the
liquid supply portion 50, the open air hole 100, the pressure
release hole 110, and the labyrinth channel defining chamber 95a,
and the sensor channel defining chamber 30b will have their
openings respectively sealed off by sealing films 54, 90, 98, 95,
35. Of these, the sealing film 90 is intended to be peeled off by
the user prior to installing the ink cartridge 1 in the carriage 6
of the ink-jet printer as described above. The open air hole 100
will thereby communicate with the outside, drawing air into the ink
cartridge 1. The sealing film 54 is designed to be ruptured by the
ink supply needle of the carriage 6 when the ink cartridge 1 is
installed in the carriage 6 of the ink-jet printer.
[0062] Inside the liquid supply portion 50 there are housed, in
order from the lower face side, a seal member 51, a spring seat 52,
and a blocking spring 53. The seal member 51 provides a seal so
that when an ink supply needle 66 is inserted into the liquid
supply portion 50, no gap will form between the inside wall of the
liquid supply portion 50 and the outside wall of the ink supply
needle 66. The spring seat 52 is adapted to abut the inside wall of
the seal member 51 and block off the liquid supply portion 50 when
the ink cartridge 1 is not installed in the carriage 6. The
blocking spring 53 urges the spring seat 52 in the direction of
abutment against the inside wall of the seal member 51. When the
ink supply needle is inserted into the liquid supply portion 50,
the upper end of the ink supply needle will push the spring seat 52
upward, producing a gap between the spring seat 52 and the seal
member 51 so that ink may be supplied to the ink supply needle
through the gap.
[0063] Next, in order to aid understanding, the pathway from the
open air hole 100 to the liquid supply portion 50 will be described
in conceptual terms with reference to FIG. 7. FIG. 7 is a
conceptual depiction of the pathway leading from the open air hole
to the liquid supply portion.
[0064] The pathway leading from the open air hole to the liquid
supply portion is broadly divided into an air introduction section
situated on the upstream side, and an ink reservoir section
situated on the downstream side.
[0065] The air introduction section includes, in order from the
upstream side, a serpentine path 310; the gas-liquid separation
chamber 70a (which houses the aforementioned gas-liquid separation
membrane 71); and connecting segments 320 to 360 that connect the
gas-liquid separation chamber 70a with the ink reservoir section.
The serpentine path 310 communicates at its upper end with the open
air hole 100, and at its lower end with the gas-liquid separation
chamber 70a. The serpentine path 310 has an elongated serpentine
shape in order to lengthen the distance from the open air hole 100
to the first ink reservoir section. Moisture evaporation from the
ink inside the ink reservoir section can be reduced thereby. The
gas-liquid separation membrane 71 is composed of a material that
allows gas to pass through but does not allow liquid to pass
through. By situating the gas-liquid separation membrane 71 between
the upstream side and the downstream side of the gas-liquid
separation chamber 70a, ink backflowing in from the ink reservoir
section can be prevented from advancing upstream beyond the
gas-liquid separation chamber 70a.
[0066] The upstream side of the ink reservoir section includes a
first ink reservoir chamber 370, a reservoir chamber connection
path 380, and a second ink reservoir chamber 390, in that order.
The upstream side of the reservoir chamber connection path 380
communicates with the first ink reservoir chamber 370, while the
downstream side of the reservoir chamber connection path 380
communicates with second ink reservoir chamber 390.
[0067] The ink reservoir section additionally includes a labyrinth
channel 400; a first flow channel 410; the aforementioned sensor
portion 30; a second flow channel 420; a buffer chamber 430; the
differential pressure regulating valve housing chamber 40a which
houses the differential pressure regulating valve 40; and a third
flow channel 450, in that order on the downstream side of the
second ink reservoir chamber 390. The labyrinth channel 400
includes a space that is defined by the aforementioned labyrinth
channel defining chamber 95a, and has three-dimensional
labyrinthine shape. Through the labyrinth channel 400, air bubbles
that have become entrained in the ink can be trapped so as to limit
entrained air bubbles in the ink to the downstream side of the
labyrinth channel 400. The first flow channel 410 communicates at
its upper end to the labyrinth channel 400, and at its lower end
communicates with the sensor channel defining chamber 30b of the
sensor portion 30. The second flow channel 420 communicates at its
upper end to the sensor channel defining chamber 30b of the sensor
portion 30, and at its lower end to the buffer chamber 430. The
buffer chamber 430 is a chamber adapted to store a prescribed
amount of ink so that a prescribed amount of printing can take
place even after there is no more ink in the sensor portion 30 and
ink depletion has been detected. The buffer chamber 430
communicates with the differential pressure regulating valve
housing chamber 40a. In the differential pressure regulating valve
housing chamber 40a, the pressure regulating valve 40 adjusts the
pressure of the ink to the downstream side of the differential
pressure regulating valve housing chamber 40a to lower pressure
than the ink on the upstream side, so that the ink on the
downstream side goes to negative pressure. The third flow channel
450 communicates at its upper end with the differential pressure
regulating valve housing chamber 40a, and at the lower end with the
liquid supply portion 50.
[0068] The liquid supply portion 50 slips around the ink supply
needle 66 which is situated on the upper face of the print head 61.
The ink contained in the liquid supply portion 50 is then supplied
to the print head 61 through the ink supply needle 66. Under the
control of the main controller 2, the print head 61 ejects the ink
supplied to it onto the paper P from nozzles NZ formed on its lower
face.
[0069] During manufacture of the ink cartridge 1 it will be filled
with ink up to the first ink reservoir chamber 370 which is
situated at the uppermost location on upstream side of the ink
reservoir section, i.e. to the liquid level shown conceptually by
the broken line ML1 in FIG. 7. As the ink inside the ink cartridge
1 is consumed by the print head 61, the liquid will flow
downstream, and consequently the liquid level will move toward the
downstream side as well, to be replaced by air inflowing into the
ink reservoir section from upstream through the air introduction
section. As the ink is progressively consumed, the liquid level
will eventually reach the sensor portion 30, i.e. the level shown
conceptually by the broken line ML2 in FIG. 7. At this point, air
will enter the sensor portion 30, whereupon the remaining liquid
level sensor module 31 will detect ink depletion. When ink
depletion is detected, the ink cartridge 1 will halt printing
before the ink present to the downstream side of the sensor portion
30 (in the buffer chamber 430 etc.) has been completely consumed,
and will notify the user that the ink is depleted. The reason for
doing so is that if the printing continues despite the ink being
completely depleted, air may be drawn into the print head 61,
possibly causing problems.
[0070] Building on the previous discussion, the specific
configuration of the elements on the pathway from the open air hole
100 to the liquid supply portion 50 inside the ink cartridge 1 will
be described with reference to FIGS. 8 to 10. FIG. 8 is a diagram
of the cartridge body 10 viewed from the front. FIG. 9 is a diagram
of the cartridge body 10 viewed from the back. FIG. 10A is
simplified schematic of FIG. 8. FIG. 10B is simplified schematic of
FIG. 9.
[0071] In the ink reservoir section, the first ink reservoir
chamber 370 and the second ink reservoir chamber 390 are formed on
the front face side of the cartridge body 10. In FIG. 8 and FIG.
10A, the first ink reservoir chamber 370 and the second ink
reservoir chamber 390 are respectively shown by single hatching and
cross hatching. The reservoir chamber connection path 380 is formed
on the back face side of the cartridge body 10, at the location
indicated in FIG. 9 and FIG. 10B. Communication hole 371 is a hole
through which the upstream end of the reservoir chamber connection
path 380 communicates with the first ink reservoir chamber 370; and
communication hole 391 is a hole through which the downstream end
of the reservoir chamber connection path 380 communicates with the
second ink reservoir chamber 390.
[0072] In the air introduction section, the serpentine path 310 and
the gas-liquid separation chamber 70a are respectively formed on
the back face side of the cartridge body 10, at the locations shown
in FIG. 9 and FIG. 10B. Communication hole 102 is a hole through
which the upstream end of the serpentine path 310 and the open air
hole 100 communicate. The downstream end of the serpentine path 310
passes through the side wall of the gas-liquid separation chamber
70a to communicate with the gas-liquid separation chamber 70a.
[0073] Turning now to a detailed description of the connecting
segments 320 to 360 of the air introduction section shown in FIG.
7, these are composed of a first space 320, a third space 340, and
a fourth space 350 (see FIG. 8 and FIG. 10A) that are situated on
the front face side of the cartridge body 10; and a second space
330 and a fifth space 360 (see FIG. 9 and FIG. 10B) that are
situated on the back face side of the cartridge body 10, with these
spaces cascaded in order of their assigned symbols from the
upstream end defining a single channel. Communication hole 322 is a
hole through which the gas-liquid separation chamber 70a
communicates with the first space 320. Communication holes 321 and
341 are respectively holes through which the first space 320
communicates with the second space 330, and the second space 330
communicates with the third space 340. The third space 340 and the
fourth space 350 communicate through a notch 342 that is formed in
the rib that divides the third space 340 and the fourth space 350.
Communication holes 351 and 372 are respectively holes through
which the fourth space 350 communicates with the fifth space 360,
and the fifth space 360 communicates with the first ink reservoir
chamber 370.
[0074] In the ink reservoir section, the labyrinth channel 400 and
the first flow channel 410 are formed on the front face side of the
cartridge body 10, at the locations shown in FIG. 8 and FIG. 10A.
Communication hole 311 is disposed in the rib that divides the
second ink reservoir chamber 390 and the labyrinth channel 400, and
connects the second ink reservoir chamber 390 with the labyrinth
channel 400. As discussed with reference to FIG. 6, the sensor
portion 30 is situated on the lower face side of the left side face
of the cartridge body 10 (FIGS. 8 to 10). The second flow channel
420 and the aforementioned gas-liquid separation chamber 70a are
respectively formed on the back face side of the cartridge body 10,
at the locations shown in FIG. 9 and FIG. 10B. The buffer chamber
430 and the third flow channel 450 are respectively formed on the
front face side of the cartridge body 10, at the locations shown in
FIG. 8 and FIG. 10A. Communication hole 312 is a hole through which
the labyrinth channel defining chamber 95a (FIG. 6) of the sensor
portion 30 communicates with the upstream end of the second flow
channel 420; and communication hole 431 is a hole through which the
downstream end of the second flow channel 420 communicates with the
buffer chamber 430. Communication hole 432 is a hole through which
the buffer chamber 430 communicates directly with the differential
pressure regulating valve housing chamber 40a. Communication hole
451 and communication hole 452 are respectively holes through which
the differential pressure regulating valve housing chamber 40a
communicates with the third flow channel 450, and the third flow
channel 450 communicates with the interior of the liquid supply
portion 50.
[0075] Here, the space 501 shown in FIG. 8 and FIG. 10A is an
unfilled chamber that is not filled with ink. The unfilled chamber
501 is not situated on the path leading from the open air hole 100
to the liquid supply portion 50, but rather is independent. An air
communication hole 502 for communicating with the outside air is
provided on the back face side of the unfilled chamber 501. The
unfilled chamber 501 functions as an air expulsion chamber for
accumulating negative pressure when the ink cartridge 1 is packaged
in a vacuum pack. By so doing, with the ink cartridge 1 in packaged
form, the pressure inside the cartridge body 10 will be maintained
at or below a prescribed value so that it can supply ink containing
negligible air in solution.
[0076] Configuration of Sensor Portion 30
[0077] The configuration of the aforementioned sensor portion 30
will be described further with reference to FIG. 11 and FIG. 12.
FIG. 11 is a diagram illustrating the configuration of the sensor
portion in first embodiment. FIG. 11 shows the A-A cross section in
FIG. 10. FIG. 12 is a diagram of the electrical configuration
centered on a piezoelectric device that included in the sensor in
first embodiment.
[0078] The aforementioned remaining liquid level sensor module 31
includes a piezoelectric device 210 constituting the sensor proper;
an oscillator plate 204, a first base plate 205, a metal plate 206,
and a second base plate 207. The piezoelectric device 210 includes
an upper electrode 201, a piezoelectric layer 202 made of
piezoelectric material such as lead zirconate titanate (PZT); and a
lower electrode 203. The oscillator plate 204 transmits oscillation
of the piezoelectric device 210 to the ink, and conversely
transmits oscillation of the ink to the piezoelectric device 210.
The oscillator plate 204 is an insulating thin film. The first base
plate 205, the metal plate 206, and the second base plate 207 are
plates having holes, and are stacked in that order. For the first
base plate 205, ceramic produced by firing a green sheet could be
used, for example. For the metal plate 206, a conductive metal such
as stainless steel could be used, for example. For the second base
plate 207, a resin could be used, for example. The oscillator plate
204 is positioned on the surface of the first base plate 205 so as
to cover the holes in the first base plate 205; and the
piezoelectric device 210 is positioned facing towards the hole of
the first base plate 205, with the oscillator plate 204
therebetween. As a result, a cavity will be defined by the holes in
the first base plate 205, the metal plate, and the second base
plate 207. As depicted in FIG. 11, viewed in A-A cross section the
cavity has a ".PI." shape.
[0079] The remaining liquid level sensor module 31 is positioned
above the sensor channel defining chamber 30b (FIG. 6) of the
cartridge body 10, as depicted in FIG. 11. As a result, the cavity
will define part of the ink reservoir section. In association with
consumption of ink by the printer, the ink inside the ink cartridge
1 will flow through the interior of the ".PI." shaped cavity as
shown by the arrows in FIG. 11. As will be appreciated from the
above description, if there is sufficient ink inside the ink
cartridge 1, that is, if the interior of the cavity depicted in
FIG. 11 is filled with ink, the conductive metal plate 206 will be
in contact with the ink filling the interior of the cavity.
[0080] The ".PI." shaped cavity (ink channel) will now be described
more specifically. In the ".PI." shaped channel, the segment along
the oscillator plate 204 is designated as the first channel; the
segment forming a generally right angle to the first channel at the
upstream end of the first channel is designated as the second
channel; and the segment forming a generally right angle to the
first channel at the downstream end of the first channel is
designated as the third channel. The piezoelectric device 210 is
situated along the first channel. A portion of the inside face of
the second channel and a portion of the inside face of the third
channel are respectively defined by the conductive metal plate 206
(FIG. 11).
[0081] The electrical configuration of the ink cartridge 1 will now
be discussed further making reference to FIG. 12. FIG. 12 depicts,
in the form of an equivalent circuit, the electrical configuration
of the ink cartridge 1 including the piezoelectric device 210.
Resistance R1 and R2 represent resistance of the ink. Electrostatic
capacitance C1 represents electrostatic capacitance produced
between the ink and the lower electrode 203 of the piezoelectric
device 210 that face one another to either side of the oscillator
plate 204, which is an insulator. This electrostatic capacitance
functions like a capacitor. Node n1 represents a node at which the
ink contacts the metal plate 206, which is a conductor. As depicted
in FIG. 12, the electrodes 201 and 203 of the piezoelectric device
210 are respectively electrically connected to one of the plurality
of electrode terminals 34a of the circuit board 34. As a result,
when the ink cartridge 1 is installed in the holder 62, the
electrodes of the piezoelectric device 210 will be electrically
connected to the carriage circuit 67 of the printer 1000.
Additionally, as shown in FIG. 12, the conductive metal plate 206
will be electrically connected to the ground terminal among the
plurality of electrode terminals 34a of the circuit board 34. As a
result, when the ink cartridge 1 is installed in the holder 62, the
metal plate 206 will be connected a stable fixed potential, namely,
the frame ground VSS of the printer 1000. Accordingly, when the
interior of the cavity is filled with ink, the ink will contact the
metal plate 206, and will be connected to the frame ground VSS via
the metal plate 206. The node n1 in FIG. 12 represents the contact
point of the ink and the frame ground VSS (i.e. the contact point
of the ink and the metal plate 206). In FIG. 12, the resistance R1
represents resistance of the ink present towards the piezoelectric
device 210 side of the cavity from the metal plate 206, that is,
between the metal plate 206 and the oscillator plate 204. In FIG.
12, resistance R2 represents resistance of the ink present on the
opposite side of the piezoelectric device 210 viewed from the metal
plate 206, e.g. the ink present in the first ink reservoir chamber
370, the second ink reservoir chamber 390, and the buffer chamber
430.
[0082] In FIG. 12, the AC power supply (noise source) indicated by
the symbol NS conceptually depicts noise propagated to the ink
inside the ink cartridge 1 from the outside.
[0083] Next, detection of the remaining ink level using the sensor
will be discussed. In the printer 1000, the main controller 2 and
the carriage circuit 67 are designed so as to be able to exchange
signals via a bus. The carriage circuit 67 has a sensor driver M1
as a function block. The main controller 2 and the sensor driver M1
of the carriage circuit 67 cooperate to carry out a process to
detect the remaining ink level in each of the ink cartridges 1
(remaining ink level detection process). Specifically, when the
main controller 2 initiates the remaining ink level detection
process, it will send to the sensor driver M1 a command requesting
frequency measurement for the purpose of determining remaining ink
level (discussed later), and data identifying the ink cartridge 1
that is to be targeted for the frequency measurement. Upon
receiving the command and the data, the sensor driver M1 will
initiate a frequency identification process on the targeted ink
cartridge 1. Specifically, the sensor driver M1 will connect, via
the corresponding electrode terminal 34a, either the upper
electrode 201 or the lower electrode 203 of the piezoelectric
device 210 to a sensor drive signal line that issues a sensor drive
signal DS. The sensor driver M1 will also connect, via the
corresponding electrode terminal 34a, the other of the upper
electrode 201 or the lower electrode 203 to the frame ground VSS.
Once the electrodes 201 and 203 of the piezoelectric device 210
have been connected to the sensor drive signal line or to the frame
ground VSS, the sensor drive signal DS will be applied to the
corresponding electrode of the piezoelectric device 210 via the
sensor drive signal line. The sensor drive signal DS is a signal
containing one or more trapezoidal pulses, for example.
[0084] When the sensor drive signal DS is applied to an electrode
of the piezoelectric device 210, strain (expansion and contraction)
will be produced in the piezoelectric device 210. Coincident with
the timing of completion of application of the sensor drive signal
DS (trapezoidal pulse), the sensor driver M1 will disconnect the
sensor drive signal line from the electrode of the piezoelectric
device 210 to which the signal line was connected. Thereupon, the
piezoelectric device 210 will oscillate (expand and contract) in a
manner dependent on the remaining ink level, and the piezoelectric
device 210 will output a voltage dependent on its oscillation (a
response signal RS) from the electrode that was disconnected from
the sensor drive signal line to the carriage circuit 67, via the
electrode terminal 34a. The sensor driver M1 of the carriage
circuit 67 will then measure the frequency of the response signal
RS.
[0085] Once the sensor driver M1 measures the frequency of the
response signal RS, the measurement result will be transmitted to
the main controller 2. On the basis of the measurement result it
has received from the sensor driver M1, the main controller 2 will
determine the remaining ink level for the ink cartridge 1 that was
targeted for the process. For example, if the remaining ink level
is equal to or greater than a prescribed level, the piezoelectric
device 210 will oscillate at a first characteristic oscillation
frequency H1 (e.g. approximately 30 KHz), whereas if the remaining
ink level is less than the prescribed level, the piezoelectric
device 210 will oscillate at a second characteristic oscillation
frequency H2 (e.g. approximately 110 KHz). Specifically, where the
remaining ink level is equal to or greater than the prescribed
level, the cavity facing the piezoelectric device 210 with the
oscillator plate 204 therebetween will be filled with ink, whereas
if the remaining ink level has fallen to below the prescribed
level, the cavity facing the piezoelectric device 210 with the
oscillator plate 204 therebetween will not contain ink, only air.
The resonance frequency of the piezoelectric device 210 will differ
to reflect such different conditions around the piezoelectric
device 210. If the frequency measurement result it has received is
substantially equal to the first characteristic oscillation
frequency H1, the main controller 2 will decide that the remaining
ink level is equal to or greater than the prescribed level, whereas
if the result is substantially equal to the second characteristic
oscillation frequency H2, it will decide that the remaining ink
level is less than the prescribed level.
[0086] According to first embodiment described above, a fixed
stable potential, namely the frame ground VSS potential, will be
applied to the ink inside the ink cartridge 1 through the medium of
the metal plate 206. As a result, interference with the
piezoelectric device 210 by outside noise with through the medium
of the conductive ink can be limited. As a result, accuracy can be
improved during detection of remaining ink level using the
piezoelectric device 210 as the electrical sensor.
[0087] In order to aid understanding, a comparative example
illustrative of the case where the ink is not connected to a stable
potential will be described with reference to FIG. 13. FIG. 13 is a
diagram of an electrical configuration centered on a piezoelectric
device that constitutes the sensor in the comparative example. In
FIG. 13, of the elements of the printer 1000a and the ink cartridge
la of the comparative example, those elements that have been
assigned like symbols to FIG. 12 are identical to the elements
assigned like symbols that were discussed in FIG. 12 and require no
further description. In the ink cartridge la of the comparative
example, resistance R3 represents resistance of the conductive ink.
In the comparative example, the part corresponding to resistance
R3, i.e. the conductive ink, functions as an antenna, receiving
noise from the outside noise source NS and transmitting it to the
piezoelectric device 210. As a result, there is a risk of the
piezoelectric device 210 oscillating due to the effects of the
noise. There is also a risk that AC noise will be propagated to the
carriage circuit 67. As a result, there is a risk that the accuracy
of detection of remaining ink level by the piezoelectric device 210
will be adversely affected. In first embodiment, interference by
such outside noise is limited.
[0088] Furthermore, as will be appreciated from FIG. 11, the metal
plate 206 is situated in proximity to the piezoelectric device 210.
That is, the ink is connected to the frame ground VSS in the
vicinity of the piezoelectric device 210. As a result, interference
by outside noise can be limited more effectively. When the location
at which ink is connected to a stable potential is situated away
from the piezoelectric device 210, the ink in a zone extending from
the contact point with the stable potential to the piezoelectric
device 210 will tend to function as an antenna and can pick up
noise, making it preferable for the ink to be connected to a stable
potential in vicinity of the piezoelectric device 210.
[0089] Furthermore, because a fixed potential is applied to the
ink, the ink itself will act as a shield so that interference of
extraneous noise with the piezoelectric device 210 can be
limited.
[0090] Additionally, as will be appreciated from FIG. 11, the metal
plate 206 defines part of the upstream side and the downstream side
of the ".PI." shaped passage as discussed above. That is, the metal
plate 206 is situated to both the upstream side and the downstream
side of the location at which the ink faces the piezoelectric
device 210 with the oscillator plate 204 therebetween (the
aforementioned first channel). As a result, the ink will be
connected to the frame ground VSS at both the upstream side and the
downstream side of the ink flowing in the vicinity of the
piezoelectric device 210. As a result, interference of extraneous
noise with the piezoelectric device 210 can be limited more
effectively.
[0091] Furthermore, since the metal plate is a component that
functions as a seat for the purpose of ensuring rigidity in the
vicinity of the piezoelectric device 210 and of limiting
attenuation of oscillation of the piezoelectric device 210, an
increase in the number of parts needed solely to connect the ink
the frame ground VSS can be avoided.
[0092] Variations of First Embodiment:
[0093] The location at which the conductive ink is electrically
connected to the frame ground VSS is not limited to a section of
the metal plate 206 as taught in first embodiment. A variation by
way of another example will be described with reference to FIG. 14.
FIG. 14 is a diagram depicting a simplified cross section of
construction in an area from the vicinity of the differential
pressure regulating valve 40 to the liquid supply portion 50, shown
together with a simplified cross section of the print head 61. In
FIG. 14, for convenience in description the structural details have
been omitted in order to aid understanding; only concise simplified
structures are depicted. The ink reservoir section is divided into
an upstream channel 213 and a downstream channel 214 by the valve
member 41 of the differential pressure regulating valve 40. The
upstream channel 213 is a section that corresponds to the upstream
side of the differential pressure regulating valve housing chamber
40a depicted in FIGS. 6 and 7. The downstream channel 214 is a
channel that leads to the liquid supply portion 50, and is composed
of the downstream side of the aforementioned differential pressure
regulating valve housing chamber 40a, and the third flow channel
450 depicted in FIG. 7. Both the upstream channel 213 and the
downstream channel 214 actual have more complex construction.
[0094] The valve member 41 is urged by the spring 42 towards the
valve seat (the left side in FIG. 14) which has been formed on the
wall face on the opposite side from the spring 42. A bypass channel
215 that communicates at a first end with the downstream channel
214 and that communicates at a second end with the wall face
defining the valve seat is also provided. When the sum of ink
pressure inside the downstream channel 214 and the force produced
by the spring 42 exceeds the ink pressure inside the upstream
channel 213, the valve member 41 will push against the valve seat
and assume the closed position. In this state, the upstream channel
213 and the downstream channel 214 are physically separated so that
ink cannot flow from the upstream channel 213 into the downstream
channel 214.
[0095] On the other hand, when the ink in the downstream channel
214 has been consumed, and the sum of ink pressure inside the
downstream channel 214 and the force of the spring 42 is now lower
than the ink pressure inside the upstream channel 213, a gap will
open up between the valve member 41 and the valve seat. As a
result, the upstream channel 213 will communicate with the bypass
channel 215, and ink will flow from the upstream channel 213 and
into the downstream channel 214 via the bypass channel 215. This
inflow of ink will continue until the sum of ink pressure inside
the downstream channel 214 and the force of the spring 42 again
counterbalances the pressure inside the upstream channel 213. When
the sum of ink pressure inside the downstream channel 214 and the
force of the spring 42 counterbalances the pressure inside the
upstream channel 213, the valve member 41 will push against the
valve seat obstructing communication between the upstream channel
213 and the bypass channel 215 so that the upstream channel 213 and
the bypass channel 215 are physically separated. Through this
design, the ink pressure inside the downstream channel 214 will be
constantly maintained at a lower level than the ink pressure inside
the upstream channel 213.
[0096] In the first variation, the valve member 41 is formed from
an electrical conductor. The electrical conductor of the valve
member 41 could be conductive rubber, a conductive elastomer, or
other conductive resin for example. Also, in the first variation,
the spring 42 that contacts the valve member 41 is also formed from
an electrical conductor. The electrical conductor of the spring 42
could be stainless steel for example. A wire is connected to the
spring 42, electrically connecting the spring 42 to the ground
terminal among the plurality of electrode terminals 34a of the
circuit board 34. As a result, when the ink cartridge 1 has been
installed in the holder 62, the valve member 41 will be connected
to the frame ground VSS in the printer 1000, which is a stable
fixed potential (the solid line in FIG. 14). When the upstream
channel 213 is filled with ink, the ink will be electrically
connected to the frame ground VSS via the valve member 41 and the
spring 42.
[0097] The above configuration affords working effects comparable
to first embodiment. Also, since the valve member 41 and the spring
42 are components that are needed anyway in to bring the ink in
proximity to the liquid supply portion 50 to negative pressure, an
increase in the number of parts needed merely to connect the ink
the frame ground VSS can be avoided.
[0098] In a second variation, as in the first variation, the valve
member 41 is formed from an electrical conductor. Meanwhile, in the
second variation, the spring is not connected to the frame ground
VSS. Instead, the ink is electrically connected to the frame ground
VSS via the print head 61.
[0099] Here, the ink supply needle 66 that pierces the liquid
supply portion 50 of the ink cartridge 1 is disposed upright on the
upper face of the print head 61. The print head 61 is provided on
its lower face with a nozzle plate 61b composed of a conductor such
as aluminum or stainless steel, and having a multitude of nozzles
NZ. The nozzle plate 61b is connected to the frame ground VSS
through a wire (the broken line in FIG. 14). In the interior of the
print head 61 there is formed an internal channel 610 that at one
end opens out from the distal end of the ink supply needle 66, and
at the other end opens into a nozzle. The ink inside the ink
cartridge 1 will flow from the end on the ink supply needle 66 side
and through the internal channel 610, to be ejected from the
nozzle. However, as the ink on the downstream side of the valve
member 41 is at negative pressure due to aforementioned valve
member 41 and spring 42, the ink will not be ejected automatically
from the nozzle hole. A piezoelectric element PZT is disposed
midway along the wall of the internal channel 610. Under the
control of the main controller 2, this piezoelectric element PZT
will expand, producing compressive deformation of the internal
channel 610 and thereby causing an ink drop IN to be ejected from
the nozzle hole. Instead of such a system whereby ink is ejected
using piezoelectric elements, it would be possible to employ a
method whereby ink drops are ejected through the action of bubbles
produced in the internal channel 610 by a heater installed within
the internal channel 610.
[0100] From the above description, it will be appreciated that the
print head 61 in this variation corresponds to the liquid jetting
section in the claims.
[0101] The downstream side from the cavity where the piezoelectric
device 210 is situated is filled with ink up to the upstream
channel 213 in FIG. 14. The ink path from the downstream channel
214 to the nozzle NZ is also filled with ink. The ink inside the
upstream channel 213 and the ink inside the downstream channel 214
are electrically connected by the valve member 41, which is a
conductor. The ink in the section furthest downstream inside the
downstream channel 214 contacts the nozzle plate 61b, and is
connected to the frame ground VSS via the nozzle plate 61b. As a
result, the ink the cavity in proximity to the piezoelectric device
210 will be electrically connected to the frame ground VSS (which
is a stable fixed potential) via the valve member 41 and the nozzle
plate 61b.
[0102] The above configuration also affords working effects
comparable to first embodiment. Also, since the valve member 41 and
the nozzle plate 61b are already necessary components of the ink
cartridge 1 and the printer 1000, an increase in the number of
parts needed merely to connect the ink the frame ground VSS can be
avoided.
[0103] The method by which the ink is electrically connected to the
frame ground VSS via the print head 61 is not limited to one of
connecting it to the frame ground VSS via the nozzle plate 61b. Any
of various components that contact the ink in the print head 61
could be fabricated from conductive material, and the conductive
member in question electrically connected to the frame ground VSS.
For example, the ink supply needle 66 in its entirety, or a portion
thereof, specifically, the distal end that contacts the ink or
section in proximity to the distal end of the ink supply needle 66
could be made of conductive material. The conductive section would
then be electrically connected to the frame ground VSS through a
wire. Alternatively, a cap made of conductive material could be
installed in the opening through which the ink in the distal end
section of the ink supply needle 66 is introduced into the internal
channel 610. The cap will have an opening to allow ink to be drawn
into the internal channel 610. The cap would then be electrically
connected to the frame ground VSS through a wire.
[0104] As shown by the first and second variations described above,
the location for electrical connection to the frame ground VSS is
not limited to the metal plate 206 as was shown in first
embodiment. That is, it is sufficient for at least part of the
inside face contacting the ink in the ink reservoir section to be
formed from a conductor, with the conductor being connected to the
frame ground VSS.
B. Second Embodiment
[0105] Printer and Ink Cartridge Configuration:
[0106] A second embodiment will be described with reference to FIG.
15 and FIG. 16. FIG. 15 is a diagram illustrating the configuration
of the sensor portion in second embodiment. FIG. 15 shows the A-A
cross section in FIG. 10. FIG. 16 is a diagram of the electrical
configuration centered on a piezoelectric device that constitutes
the sensor in second embodiment.
[0107] The simplified configurations of the printer 1000b and the
ink cartridge 1b in second embodiment are the same as those of the
printer 1000 and the ink cartridge 1 in first embodiment described
previously with reference to FIGS. 1 to 10, and thus require no
further description; in the following discussion, like elements
will be assigned like symbols.
[0108] The ink cartridge 1b of second embodiment differs from the
ink cartridge 1 of first embodiment 1 in terms of the configuration
of the sensor portion. As depicted in FIG. 15, the sensor portion
30 of second embodiment is provided with a remaining liquid level
sensor module 31b in place of the remaining liquid level sensor
module 31 of first embodiment.
[0109] The remaining liquid level sensor module 31b of second
embodiment is provided with a thin insulating film 211 and a thin
conducting film 212, in addition to a piezoelectric device 210, an
oscillator plate 204, a first base plate 205, a metal plate 206,
and a second base plate 208 comparable to those in first
embodiment. The thin insulating film 211 and the thin conducting
film 212 are positioned between the piezoelectric device 210 and
the oscillator plate 204. The thin insulating film 211 is
positioned towards the piezoelectric device 210 side, and the thin
conducting film 212 is positioned towards the oscillator plate 204
side. The configuration of the remaining liquid level sensor module
61b of second embodiment is otherwise the same as the remaining
liquid level sensor module 31 of first embodiment, and requires no
description. An insulating layer (the thin insulating film 211), a
conducting layer (the thin conducting film 212), and an insulating
layer (the oscillator plate 204) are stacked between the ink from
the piezoelectric device 210 in that order, going towards the ink.
As depicted in FIG. 16, the thin conducting film 212 is connected
to the ground terminal among the plurality of electrode terminals
of the circuit board 34. As a result, when the ink cartridge 1b is
installed in the holder 62, the thin conducting film 212 will be
connected to a stable fixed potential in the printer 1000b, namely,
to the frame ground VSS.
[0110] The electrical configuration of the ink cartridge 1b will be
discussed further with reference to FIG. 16. FIG. 16 depicts, in
the form of an equivalent circuit, the electrical configuration of
the ink cartridge 1b including the piezoelectric device 210. As in
FIG. 13, resistance R3 represents resistance of the ink.
Electrostatic capacitance C3 represents electrostatic capacitance
produced by the thin conducting film 212 and the lower electrode
203 of the piezoelectric device 210 that face one another to either
side of the thin insulating film 211. Electrostatic capacitance C4
represents electrostatic capacitance produced by the ink and the
thin conducting film 212 that face one another to either side of
the oscillator plate 204, which is an insulator. Node n2
corresponds to the thin conducting film 212, and show that the thin
conducting film 212 is connected to the frame ground VSS via an
electrode terminal 34a.
[0111] According to second embodiment described above, in the
cavity of the remaining ink level sensor module 31b, the ink is AC
connected via electrostatic capacitance C4 to the frame ground VSS,
which is a stable potential. As a result, interference with the
piezoelectric device 210 by the AC component of the electrostatic
capacitance C4 through the medium of the conductive ink can be
limited. As a result, the sensing accuracy of the piezoelectric
device 210 when used as an electrical sensor for detecting
remaining ink level can be improved, for example.
[0112] Manufacture of the remaining ink level sensor module 31b is
relatively simple, since it involve simply increasing the number of
layers in the stack by two.
[0113] Furthermore, since the thin conducting film 212 does not
come into direct contact with the ink, it is not necessary to
consider the ink resistance (resistance to corrosion by ink, etc.)
of the thin conducting film 212, and inexpensive materials may be
used. The risk of ink leakage due to corrosion of the thin
conducting film 212 is also eliminated.
[0114] Variations of Second Embodiment:
[0115] The location at which the ink is electrically connected to
the frame ground VSS with electrostatic capacitance therebetween is
not limited to the vicinity of the remaining ink level sensor
module 31b as taught in second embodiment. A variation by way of
another example will be described with reference to FIGS. 17 and
18. FIG. 17 is an exploded perspective view of an ink cartridge in
a variation of second embodiment. FIG. 18 is a diagram of the
electrical configuration centered on a piezoelectric device that
constitutes the sensor in the variation of second embodiment. The
ink cartridge 1c of the variation depicted in FIG. 17 differs from
the ink cartridge 1 of first embodiment 1 depicted in FIG. 5 in
that the front face side of the cartridge body 10 is covered by a
film. In the ink cartridge 1 of first embodiment 1, a single film
80 is adhered to the edge faces of the front end side of the ribs
10a of the cartridge body 10 (FIG. 5). On the other hand, in this
variation, one insulating film 81 is adhered to the edge faces of
the front end side of the ribs 10a of the cartridge body 10, and
additionally a conducting film 82 of approximately the same size is
then placed on and adhered to the insulating film 81. That is, the
wall of the ink cartridge 1 is formed by the insulating film 81 and
the conducting film 82, with the insulating film 81 situated on the
side of the wall that contacts the ink (the inner side) and the
conducting film 82 situated on the side opposite the ink (the outer
side). For the insulating film 81, an insulating resin film could
be used, for example. For the conducting film 82, aluminum foil
could be used, for example.
[0116] The electrical configuration of the ink cartridge 1c will
now be discussed further making reference to FIG. 18. FIG. 18
depicts, in the form of an equivalent circuit, the electrical
configuration of the ink cartridge 1c including the piezoelectric
device 210. Resistance R4 and R5 represent resistance of the ink.
Electrostatic capacitance C1 represents electrostatic capacitance
produced by the ink and the lower electrode 203 of the
piezoelectric device 210 that face one another to either side of
the oscillator plate 204, which is an insulator. Electrostatic
capacitance C5 represents electrostatic capacitance produced by the
ink and the conductive film 82 that face one another to either side
of the insulating film 81. As shown by the equivalent circuit, the
ink resistance R4 and R5, and the electrostatic capacitance C5,
branch at a node n3 and have a mutually parallel relationship. As
depicted in FIG. 18, the conductive film 82 is electrically
connected to one of the plurality of electrode terminals of the
circuit board 34. As a result, when the ink cartridge 1c has been
installed in the holder 62, the conductive film 82 will be
electrically connected to the frame ground VSS of the printer
1000c.
[0117] According to the variation described above, since the
electrostatic capacitance C5 will absorb extraneous noise,
interference of the AC component of extraneous noise with the
piezoelectric device 210 through the medium of the conductive ink
can be limited. As a result, where for example the piezoelectric
device 210 is used as an electrical sensor to detect remaining ink
level, accuracy can be improved.
[0118] Furthermore, in this variation, the conducting film 82 and
the insulating film 81 that form the electrostatic capacitance CS
constitute the wall corresponding to one face of the ink cartridge
1c, which is a hollow, generally rectangular parallelepiped. As a
result, as depicted in FIG. 17, the insulating film 81 and the
conducting film 82 substantially cover a parallel projection plane
of the ink inside the ink cartridge 1c viewed from the Y axis
direction (FIG. 17). Accordingly, AC noise interfering with the ink
can be efficiently absorbed from the ink as a whole.
[0119] For the conducting film 82 and the insulating film 81, a
ready-made aluminum laminate composed of aluminum foil and an
insulating resin film could be used as well.
[0120] In this variation, one entire face of the generally
rectangular parallelepiped ink cartridge 1c is covered by the
conducting film 82 and the insulating film 81; however, it is not
necessary for the entire face to be covered, and it would be
acceptable to cover only a portion.
C. Other Variations
[0121] (1) In the preceding embodiments and their variations, ink
cartridges of open-air design whereby air is drawn into the ink
reservoir section as the ink is consumed were employed; however,
the present invention is not limited to being implemented in such
designs. The invention could be implemented analogously, for
example, in ink cartridges of hermetic design in which the ink is
contained in a sealed container, with the container shrinking as
the ink is consumed. An example of an ink cartridge of hermetic
design will be described with reference to FIGS. 19 to 21. FIG. 19
depicts a hermetic type ink cartridge in front view and in side
view. FIG. 20 is a first diagram depicting the B-B cross section in
FIG. 19. FIG. 21 is a second diagram depicting the B-B cross
section in FIG. 19, FIG. 20 depicts a cross section in the case
where the remaining ink level in the ink cartridge 1d is greater
than a prescribed level; and FIG. 21 depicts a cross section in the
case where the remaining ink level in the ink cartridge 1d is less
than a prescribed level.
[0122] As depicted in FIG. 19, the ink cartridge Id includes a
generally rectangular parallelepiped hollow housing 20d; an ink
pack 10d housed inside the housing 20d; an ink supply tube 51d; and
a remaining ink level sensor module 31d. The housing 20d is made of
resin, for example. The ink pack 10d is constructed in pouch form
by joining together two pliable, generally rectangular synthetic
resin films 10d.sub.--u and 10d.sub.--b. The interior of the ink
pack 10d is filled with conductive ink. The ink supply tube 51d is
affixed to one face of the housing, with the other end of the ink
supply tube 51d exposed to the outside. An ink supply hole 50d
opens at the outside end of the ink supply tube 51d.
[0123] When the ink cartridge 1d is installed in a printer (not
shown), the ink supply needle which communicates with the print
head of the printer will slip into the ink supply hole 50d of the
ink cartridge 1d. In response to ejection of ink from the nozzle by
a piezo element inside the print head of the printer, the ink will
pass from the ink pack 10d and through the ink supply tube 51d, to
be supplied to the print head from the ink supply hole 50d.
[0124] The remaining ink level sensor module 31d is situated midway
along the ink supply tube 51d. Like the remaining ink level sensor
module 31 in first embodiment, the remaining ink level sensor
module 31d is used to determine whether the remaining level of ink
stored in the ink cartridge 1d is above a prescribed level, or
below the prescribed level.
[0125] As in first embodiment, the remaining ink level sensor
module 31d includes a piezoelectric device 210 that includes an
upper electrode 201d, a piezoelectric layer 202d, and a lower
electrode 203d. Also, as in first embodiment, the remaining ink
level sensor module 31d is additionally furnished with an
oscillator plate 204d, a first base plate 205d, a metal plate 206d,
and a second base plate 207d. These constituent elements 210d and
204d-206d are stacked in the same order as in the remaining ink
level sensor module 31 in first embodiment. Moreover, like the
metal plate 206 (FIG. 11) of first embodiment, with the ink
cartridge 1 installed in the printer the metal plate 206 is
electrically connected to the frame ground VSS of the printer.
[0126] The remaining ink level sensor module 31d is connected to an
upper film 10d.sub.--u that makes up the pouch-shaped ink pack 10d.
A spring 216d is disposed between the remaining ink level sensor
module 31d and the lower film 10d.sub.--b that makes up the ink
pack 10d. The spring 216d applies stress to the remaining ink level
sensor module 31d and to the lower film 10d.sub.--b, in the
direction of expansion of the space between the remaining ink level
sensor module 31d and the lower film 10d.sub.--b.
[0127] If the remaining ink level in the ink pack 10d is greater
than a prescribed level, the ink pack 10d will be pushed and spread
out by the spring 216d, thereby forming a relatively wide space
filled with ink below the piezoelectric device 210d as depicted in
FIG. 20. On the other hand, if the remaining ink level in the ink
pack 10d is less than a prescribed level, the ink pack 10d, the
spring 216d will be compressed due to compression of the spring
216d, thereby forming a relatively narrow space filled with ink
below the piezoelectric device 210d as depicted in FIG. 21.
[0128] Detection of remaining ink level in the ink cartridge 1d of
hermetic design will now be described. Like the ink cartridges of
open-air design described in the preceding embodiments, a sensor
drive signal DS is applied to the piezoelectric device 210d from
the printer end. Thereupon, as in the ink cartridges of open-air
design, the piezoelectric device 210d will oscillate (expand and
contract) in a manner dependent on the remaining ink level and will
output an oscillation-dependent voltage (response signal RS) to the
printer. At this point, in the ink cartridge of open-air design,
the frequency of the response signal RS would be measured to
determine the remaining ink level; in the hermetic ink cartridge,
however, the remaining ink level is determined by measuring the
magnitude of the amplitude of the response signal RS. Specifically,
if the remaining ink level is above the prescribed level, i.e. if a
relatively wide space filled with ink is formed below the
piezoelectric device 210d, the amplitude of the response signal RS
will be greater. Conversely, if the remaining ink level is below
the prescribed level, i.e. if a relatively narrow space filled with
ink is formed below the piezoelectric device 210d, the amplitude of
the response signal RS will be smaller. Accordingly, if the
amplitude of the response signal RS is greater than a prescribed
value, it will be determined that the remaining ink level in the
ink pack 10d is above the prescribed level, whereas if the
amplitude of the response signal RS is less than a prescribed
value, it will be determined that the remaining ink level in the
ink pack 10d is below the prescribed level.
[0129] In the ink cartridge 1d of the variation described above,
the ink inside the ink cartridge 1d is electrically connected to
the frame ground VSS via the metal plate 206. As a result, the ink
cartridge Id of the variation affords working effects comparable to
first embodiment.
[0130] (2) In the above embodiments and variations, the
piezoelectric device used as the sensor is disposed in the ink
cartridge; however, it would also be acceptable to dispose it on
the printer end, for example, along the ink channel that leads to
the nozzle in the interior of the print head of the printer.
Specifically, like the remaining ink level sensor module 31m shown
by the broken lines in FIG. 14, the sensor could be situated on the
internal channel 610 that leads from the ink supply needle 66 to
the nozzle NZ in the print head 61, for example. In this way, the
sensor may be disposed in a part of the space which leads from the
ink cartridge interior and ink supply needle to the nozzle and in
which ink is present. As will be appreciated from the above
description, the liquid reservoir section taught in the claims
corresponds to the space which leads from the ink cartridge
interior and ink supply needle to the nozzle and in which ink is
present, taught in above-mentioned embodiments.
[0131] (3) In the above embodiments and variations, the ink
cartridge is detachably installed in the printer; however, an ink
tank that is affixed to the printer could be used instead. As will
be appreciated from the preceding embodiments, the combination of
the ink cartridge and the printer taught in above-mentioned
embodiments corresponds to the liquid jetting apparatus taught in
the claims.
[0132] (4) In the preceding embodiments, an ink-jet printer and an
ink cartridge for ink-jet printer use were employed, but it would
be possible to instead employ a liquid jetting apparatus that jets
or ejects some other liquid besides ink, and a liquid container for
use in such a liquid jetting apparatus. Herein, the term liquid is
used to include liquids in which particles of functional material
have been dispersed in a medium; or fluids such as gels. Examples
would be liquid jetting apparatus that jet fluids containing in
dispersed or dissolved form materials such as electrode materials
or coloring matter used in the manufacture of liquid crystal
displays, EL (electroluminescence) displays, surface emitting
displays, or color filters; liquid jetting apparatus used for
jetting liquids containing bioorganic substances used in biochip
manufacture; or specimen jetting devices used as precision
pipettes. Further examples are liquid jetting apparatus used for
pinpoint application of lubricants in precision instruments such as
clocks or cameras; liquid jetting apparatus for jetting ultraviolet
curing resins or other transparent resin solutions onto a substrate
for the purpose of forming a micro semi-spherical lens (optical
lens) for use in optical communication elements etc.; or liquid
jetting apparatus for jetting acid or alkali etchant solution for
etching circuit boards etc. The present invention is applicable to
any of the above types of liquid jetting apparatus and to liquid
containers for these liquid jetting apparatus.
[0133] (5) In the preceding embodiments, a piezoelectric device was
employed as the sensor, but other types of sensor could also be
used. For example, a type of sensor that measures the resistance of
ink when an electrical current is passed through the ink would be
acceptable. Nor is the sensor limited to one that detects remaining
ink level; sensors that electrically detect ink viscosity, type,
density etc. could be used as well. Generally speaking, any sensor
for the purpose of electrically detecting the condition of a liquid
such as ink is acceptable.
[0134] (6) In first embodiment and its variations, the metal plate
206, the valve member 41, and the nozzle plate 61b are disposed in
contact with the ink; and the metal plate 206, the valve member 41,
and the nozzle plate 61b are connected to a stable potential.
However, this arrangement is not limiting, and any kind of
conductor could be connected to the ink at any location in the ink
reservoir section, with the conductor being electrically connected
to a stable potential. For example, in FIG. 5, the film 80 that is
used to form the chamber housing the ink inside the ink cartridge 1
could be a conductive film, and the conductive film electrically
connected to the frame ground VSS. By so doing, the conductive film
will substantially cover a parallel projection plane of ink inside
the ink cartridge 1 viewed from the Y axis direction (FIG. 5), so
interference by extraneous noise with the ink can be effectively
limited
[0135] (7) In the variation of second embodiment, the cartridge
body is covered by a laminate composed of an insulating film 81 and
a conducting film 82 in order to form electrostatic capacitance for
the purpose of eliminating noise, but no particular limitation is
imposed thereby. For example, of the cartridge body, the portion
that forms the chamber housing the ink could be a thin section, and
a conductor could be disposed to the outside of the thin section,
with the conductor connected to the frame ground VSS. Generally
speaking, in the ink reservoir section, the inside face that
contacts the ink may be formed at least in part by an insulator,
and a conductor may be disposed to the opposite side of the
insulator from the inside face thereof that contacts the ink, with
the conductor being connected to a stable potential.
[0136] (8) In the above embodiments and variations, the ink or
electrostatic capacitance for the purpose of eliminating noise is
connected to the frame ground VSS, but no particular limitation is
imposed thereby, and connection to any fixed or stable potential
would be acceptable. Specifically, connection to signal ground or
earth potential would be acceptable.
[0137] (9) In the above embodiments, the shape of the ink
cartridge, including the first and second ink reservoir chambers
and the buffer chamber, are identified specifically; however, these
are merely exemplary, and modifications and improvements thereto
will be apparent to the skilled practitioner.
[0138] While the print control technology pertaining to the
invention have been shown and described on the basis of the
embodiments and variations, the embodiments of the invention
described herein are merely intended to facilitate understanding of
the invention, and implies no limitation thereof. Various
modifications and improvements of the invention are possible
without departing from the spirit and scope thereof as recited in
the appended claims, and these will naturally be included as
equivalents in the invention.
* * * * *